In a typical internal combustion engine, rocker levers each cooperate with a respective valve and with a respective push rod which, during axial movement, brings about a movement of the valve against the urging of a closure spring. Each such push rod is moved by a driving cam carried by a control shaft and by a double-armed intermediate lever, one arm of which engages the push rod and the other arm of which is engaged by the driving cam. The point of engagement of a first intermediate lever with the periphery of the driving cam is offset relative to the point of engagement of a second intermediate lever therewith by a specific angular amount when the control shaft is arranged to rotate in one direction.
Actuating the inlet and exhaust valves in an internal combustion engine with two rocker levers operated in common by a driving cam of a control shaft is inexpensive and is economical in space. However, some applications require that the engine crankshaft rotate in one direction, while other applications require that the crankshaft rotate in the opposite direction. Rather than manufacturing two entirely different engines for the two types of applications, it is desirable that a single basic engine be manufactured and be capable of adaptation for use in either type of application. If, however, the direction of shaft rotation is to be variable in the same type of engine (counterclockwise rotation or clockwise rotation), there are difficulties because, in a valve actuating arrangement of the type mentioned, the ducts associated with the valves (the inlet duct and the exhaust duct) are of different shape and therefore are not readily functionally interchangeable when the direction of rotation is reversed. This results in poor loading, performance and so on when there is a reversal of a rotational direction. Moreover, in such instances, the positions of the air filter, the exhaust conduit and so on are dependent on the direction of rotation, as a result of which troublesome mechanical alterations are needed for a change from one direction of shaft rotation to the other.
It is an object of the present invention to overcome these drawbacks and provide a mechanism for actuating the valves of an internal combustion engine which facilitates a changeover from one direction of rotation of the crankshaft to the other with a minimum expenditure of resources and without disadvantages in output resulting from the changeover.